If you're living far enough from the equator in either direction, winter can be tough. It can leave you stuffy-nosed, dry-skinned, a few pounds heavier, and less enthusiastic about life than you were when the days were warmer, longer, and sunnier. Seasonal affective disorder, also known as SAD, is a very real condition, and many of us are dealing with its symptoms right now.

But how do you know if your low mood and lethargy are the winter blues or something more serious and long-standing? Where is the line between SAD and depression? I asked Michel Mennesson, M.D., a psychiatrist who likes to take a holistic approach to mental health—often integrating mindfulness principles into his treatment protocols—these very questions to help us all distinguish between the two.

How to tell the difference between SAD and depression.

According to Dr. Mennesson, if your low mood comes and goes with the cold weather, it's a telltale sign that you're suffering from SAD. But it's not quite that simple because not all SAD starts at the same time of year. "Generally, most people who suffer from SAD start feeling symptoms in the fall. SAD symptoms usually continue through the winter and ease up or disappear once the warm weather returns. But for others, SAD may come on in spring," he explained.

SAD and depression have many overlapping symptoms—which is why it's often hard to tell the difference—but Dr. Mennesson explains that there are some telltale signs and symptoms of SAD that are not often seen in regular depression, including:

Being extra sensitive to rejection (not typical of depression)

Oversleeping (usually you see difficulty falling asleep in depression)

Having cravings for foods high in carbohydrates

Suffering from weight gain (weight loss is more typical in regular depression)

Experiencing a heavy feeling in the arms or legs

Interestingly, younger people and women are at higher risk for sad. In fact, three-quarters of people diagnosed with SAD are female.

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Why it's so important to distinguish between SAD and depression.

So many of the symptoms of SAD and depression overlap—SAD is just seasonal depression, after all—so why is it so important to figure out what's what? According to Dr. Mennesson, knowing the difference between depression and SAD allows the person suffering to find out what type of treatment or interventions they need. "While some interventions can be helpful for both, some are less so; for example, light therapy is particularly effective for SAD, while medication may not be as effective for SAD as for regular depression." In other words, in order to avoid unnecessary medication or treatments that will not work, you need to know what the root cause of your depression really is. And most importantly, this isn't something you should necessarily self-diagnose. Your doctor can help you tell the difference and create a treatment plan tailored to you.

That said, there is one avenue of treatment that is bound to improve your mental health—and that's a mindfulness practice. "Whether it’s SAD or depression, developing a mindfulness practice is proven to decrease symptoms and lift mood by shifting the mind and body into parasympathetic ("rest and digest") mode."explained Dr. Mennesson, who is an an avid yogi and meditator himself.

So what's the take-home? Neither SAD nor depression are conditions that you should feel like you need to handle alone. Reach out to a doctor, a friend, or a therapist or counselor, and make sure you're getting the support you need—whether you need it all year round or just in the winter months.